Kelp bed community shifts following sea star wasting syndrome in Howe Sound, British Columbia
Bibliographic record
Abstract
Echinoderm population cycles may be important drivers of ecological shifts on kelp bed communities. In Howe Sound, British Columbia, kelp beds are dominated the perennial Agarum fimbriatum, which provides important habitat for a variety of fish and invertebrates. The northeast Pacific recently experienced a mass mortality of sea stars beginning in early September 2013, and the sunflower star Pycnopodia helianthoides – a previously abundant predator of bottom-dwelling invertebrates –disappeared from many sites in a matter of weeks. By comparing the abundance of invertebrates and kelp before and after the sea star mortality event, we observed a four-fold increase in the abundance of green sea urchins and a 50% decline in kelp cover. Surveys were conducted during summer when Agarum blade size and growth is greatest. Here, we present the hypothesis that some of the changes we observed resulted from a trophic cascade involving sea stars, urchins and kelp. Behavioural experiments conducted in situ suggest predation release as a key mechanism underpinning the shift in urchin numbers. To quantify the impact of higher urchin abundance on kelp, we conducted 10 independent grazing experiments where A. fimbriatum was transplanted to barren rocky reefs of various green urchin densities. At high densities, kelp declined more that 40% in as little as 24 hrs. A. fimbriatum also provides key settlement habitat for the spot prawn Pandalus platyceros, so we predict the trophic cascade may impact spot prawn abundance in future years. Keywords: algae, trophic cascade, echinoderm, sea star wasting, mass mortality event
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".